In recent years, proposals have been made with regard to services (for watching or listing to contents) that allow digital contents of digital broadcasts to be stored for subsequent use (playing, editing, and so on) at a receiver end, by use of a large-volume storage device such as a hard-drive that allows random access. Such services will be realized by storing contents in a randomly accessible storage device, thereby allowing a scene of a particular content (i.e., a scene of a user-requested content) to be played on a random-access basis.
Contents of digital broadcasts include metadata corresponding to each scene. The metadata refers to information about contents, and is typically comprised of intra-program indexes equivalent to the headings of scenes in a given program. Contents having metadata attached thereto are transmitted from the transmission side, and the metadata is then utilized on the reception side for content search (i.e., search for particular scenes in the contents).
While the services that are realized based on the contents stored in randomly accessible storage devices offer great convenience to viewers/listeners (hereinafter referred to simply as viewers) at the receiving end, broadcasting stations (i.e., content providers) on the transmission side may have to tolerate the use of contents in the manner that have never been intended (i.e., the illegal use of contents). For example, part of the contents such as commercials may be skipped (erased) on purpose for the convenience of viewers. In other examples, metadata attached to the contents on the transmission side may be tampered by viewers with malicious intent on the receiver side, or may be changed to another metadata for the purpose of using contents (i.e., unauthorized use of the contents).
In order to prevent such illegal use of contents, control signals that prohibit the skipping of scenes and/or commercials in contents may be transmitted from the transmission side by multiplexing such control signals with the contents. On the reception side, the receiver is controlled to operate according to the received control signals so as to let the viewers to watch the contents.
Such measure to prevent the illegal use of contents is based upon the control of the receiver device according to the control signals multiplexed on the transmission side. The receiver, however, may be rigged, or may be a product manufactured specifically for the purpose of illegal use. In such a case, the control signals multiplexed on the transmission side may not function as originally intended.
Accordingly, there is a need for a transmission/reception scheme that can prevent the illegal use of contents even when the receiver is rigged, or is a product specifically made for illegal use.